Electronic devices are available to perform a variety of functions. Generally, the electronic devices have a plurality of electronic components therein that are physically attached to, or mounted on, a structure referred to as a “motherboard” or a “circuit board.” During assembly, the motherboard is secured within a protective housing, chassis or the like. Depending upon the nature of the electronic device, various user interface devices (buttons, knobs, switches, displays or the like) and connection interfaces to other electronic devices are disposed on the outside surfaces of the protective housing, chassis or the like.
One commonly encountered electronic component is the Integrated Circuit (IC). The IC has a die therein which is an electronic chip comprising a plurality of semiconductor elements therein which form one or more electronic circuits. Typically, many dies are fabricated onto a relatively large silicon wafer. Individual dies are then cut (diced) away from the silicon wafer, and are then individually packaged onto a carrier structure to form an IC. The carrier structure of the ICs includes a plurality of electrical connectors that provide electrical connectivity between the electronic circuits of the die and connectors on the motherboard, thereby providing a means for electrical connectivity to other electronic components also attached to the motherboard. The IC may be attached to the motherboard in a variety of manners, such as by using solder type connections or push pin connectors.
Of particular interest to the electronic industry is a particular type of IC known as a “flip chip” IC package, or the flip chip. The flip chip is based on a fabrication process wherein during fabrication of the die on the silicon wafer, one or more electrical contacts are directly fabricated into the silicon wafer material. These electrical contacts provide an electrical connection from a formed semiconductor electronic circuit of the die to the outside surface of the die (which is typically to the top surface of the dies formed on the silicon wafer). Once formed, small solder bumps, solder balls or the like are affixed to the surface of the die at each of the electrical contacts that are exposed on the top of the die surface.
Then, the die is “flipped” over and placed onto a carrier structure with electrical connectors fabricated therein. When placed upside down on the carrier structure, the solder bumps, balls or the like are aligned with and are in contact with corresponding electrical connectors of the carrier structure. When a soldering process is performed, the upside down die becomes secured to the carrier structure. Then, an underfill material that fills in the areas under the die between the carrier and the solder bumps, balls or the like is applied. Accordingly, the carrier structure and underfill material provides physical protection and support to the relatively fragile die. The carrier structure facilitates attachment to the motherboard since the carrier structure electrical connectors are readily accessible for connecting to the corresponding electrical connectors of the motherboard. This upside down die attached to the carrier substrate is referred to as a flip chip.
Some types of ICs, during operation, generate undesirable levels of heat which must be transferred away from the IC to prevent damage to the IC and/or to other nearby electronic components. A heat absorbing and dissipating structure, referred to herein as a heat sink, may be placed in thermal contact with the heat-generating IC. The heat generated by the IC is absorbed by the heat sink, is thermally conducted away from the IC and to another portion of the heat sink, and then is dissipated out from the heat sink as thermal energy. Such heat sinks are typically added after the IC has been attached to the motherboard.
FIG. 1 is a perspective view 100 of a legacy heat sink 102 being affixed over a flip chip 104 that is secured to a motherboard 106. The flip chip includes the carrier structure 108, the upside down die 110, and the underfill 112. The legacy heat sink 102 is secured to the motherboard 106 using a plurality of suitable fasteners, such as the example push pin connector assemblies 114. Each example push pin connector assembly 114 includes a head 116, a retainer pin 118, a lock tab structure 120, and a coiled spring 122.
The legacy heat sink 102 is affixed to the motherboard 106 by a person or machine. The lock tab structure 120 of each of the push pin connector assemblies 114 is aligned with a corresponding bore 124 (a hole) that extends through a top surface 126 to a bottom surface 128 of the motherboard 106. When the lock tab structure 120 is aligned with the respective bore 124, a downward force is exerted on the heads 116 of the push pin connector assemblies 114, thereby moving the lock tab structure 120 through the respective bore 124. When the lock tab structure 120 has passed through the bore 124, the lock tab structure 120 engages the bottom surface 128 of the motherboard 106 so as to become non-retractable, and thereby affixing the legacy heat sink 102 to the motherboard 106. The coiled spring 122, which has been compressed while the lock tab structure 120 is passing through the bore 124, maintains a force or pressure so that the bottom surface of the legacy heat sink 102 remains in thermal contact with the top of the flip chip 104. Thus, heat generated by the operating flip chip 104 can be absorbed and dissipated by the legacy heat sink 102.
FIG. 1 further illustrates a problem often encountered when a legacy heat sink 102 is affixed to the motherboard 106. The problem arises when the lock tab structure 120 of a plurality of push pin connector assemblies 114 are not evenly pushed through their respective bores 124 of the motherboard 106. That is, and as illustrated in FIG. 1, the legacy heat sink 102 may be at some point be disposed at an angle θ1 relative to the orientation of the motherboard 106.
As illustrated in FIG. 1, when the legacy heat sink 102 is affixed to the motherboard 106 at an example angle θ1 (illustrated as being approximately 15°), the bottom surface of the legacy heat sink 102 will be in contact with an edge of the top surface of the die 110 of the flip chip 104. In such situations, an undesirable amount of force and/or pressure may be applied to this edge of the die 110. Such applied force or pressure may be sufficient to cause damage to the relatively fragile die 110. For example, the edge and/or a corner of the top surface of the die 110 may become crushed, and/or a crack may be caused through the die 110. If sufficient damage occurs to the die 110, the die 110 may become inoperable.
Accordingly, there is a need in the arts to provide a system and method for limiting the travel distance, and hence the angle, of a heat sink when the heat sink is affixed to the motherboard 106 over the flip chip 104.